<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" href="./css/main.css">
</head>

<body>

    <div class="dialog" id="addDialog">
        <div class="content">
            this is content
            <span id="close" class="close">X</span>
        </div>
    </div>

    <script>
        const closeBtn = document.getElementById('close');
        const addDialog = document.getElementById('addDialog');
        closeBtn.onclick = function () {
            addDialog.style.display = 'none';
        }
    </script>

</body>

</html>